This is through process of elimination:
We already know it was in servlet spec 2.3
For servlet spec 2.1:
http://java.sun.com/products/servlet/2.1/servlet-2.1.pdf - Nothing about web.xml here
So it must have been spec 2.2
Which would make it the j2ee 1.2.1 specification
and JSP at that time was jsp 1.1